The present inventions relate generally to wireless communications antenna systems. In particular, they relate to improvements in actuators for adjusting attributes of wireless base station antennas.
Wireless mobile communication networks continue to evolve given the increased traffic demands on the networks, the expanded coverage areas for service and the new systems being deployed. Cellular (“wireless”) communications networks rely on a network of base station antennas for connecting cellular devices, such as cellular telephones, to the wireless network.
Many base station antennas include a plurality of radiating elements in a linear array. Various attributes of the antenna array, such as beam elevation angle, beam azimuth angle, and half power beam width may be adjusted by electrical-mechanical controllers. See, for example, U.S. Pat. Nos. 6,573,875, 6,603,436 and 8,674,787, the disclosures of which are incorporated by reference. In these examples, differential phase shifters may be activated by linearly-reciprocal linkages. The phase shifters may, for example, adjust electrical down tilt by changing the phase relationships in a vertically-oriented, phased array of radiating elements. In other examples, phased arrays may steer beams in the azimuth direction, or phase shifters may be used with hybrid circuits to adjust power division and/or beam width.
In one example of a phase shifter as described in U.S. Pat. No. 8,674,787, a phase shifter assembly includes a phase shifter carrier, a phase shifter printed circuit board mounted on the first phase shifter carrier, a wiper printed circuit board coupled to an input of the phase shifter printed circuit board and having at least a first end coupled to transmission lines on the phase shifter printed circuit board, and a wiper support mechanically coupling the first wiper printed circuit board to the phase shifter printed circuit board. Actuating elements may include a pivot arm and a throw arm. The pivot arm may be rotatably mounted in the phase shifter assembly and be configured to engage a wiper support of at least one of the first and second phase shifter sub-assemblies. The pivot arm may further have a slot oriented substantially parallel to a longitudinal axis of the pivot arm. The throw arm may be mounted to the phase shifter assembly to allow linear movement of the throw arm, the throw arm further having a pin that engages the slot of the pivot arm such that when the throw arm is moved linearly, the pivot arm rotates around a pivot. In this way linear movement of the throw arm is translated into rotational movement of the pivot arm, resulting in rotational movement of the wiper arms. The throw arm may be extended for a bottom of an antenna so that it may be manually or remotely electrically operated by an actuator.
While such phase shifter assemblies work well, increasing demands for additional band width and additional operating bands are creating difficulties. For example, a multiband antenna could require as many as six more electrical actuators to adjust down tilt of each RF band independently of each other. Including numerous, remote electrical tilt actuators results in undesirable levels of crowding, expense, and wiring difficulties at the bottom of the antenna.